In the system described in the prior art U.S. Pat. No. 4,880,333, a plurality of core sheets of identical geometry are wrapped serpentine fashion with a geotextile fabric so as to provide a continuous horizontally extending stack of in-drains in an excavation that preferably includes a layer of sand and other fill so that leachate can be fed from a septic system or tank through a fluid conduit provided above the stack of in-drains for purposes of distributing the leachate downwardly through openings in the overlying fluid conduit means in an efficient fashion.
It has been found that when identical core sheets of this type are stacked together with a geotextile fabric being the only separation between them, that back filling and/or handling of this setup tends to cause the initially separated core sheets with the wrapped geotextile fabric, to be compressed one core sheet nesting into the other, leading to areas of the overall system which fail to serve their intended purpose.
The general object of the present invention is to provide an improved stack of such in-drains comprising core sheets and overwrapped geotextile fabric that avoid this propensity for compression during the back filling and/or handling operation (installation).